Hi
As someone with Stage 4 Lung cancer I suffer from the same problem. I have travelled, since diagnosis, to Russia, Cambodia, Vietnam, Burma, Canada, America, France, Ireland, and got back from New Zealand yesterday. In June I am off to Germany and Hungary.
And Leah is right. We can't get insurance for things related to our pre existing condition. It's a bummer but I just take the risk. And keep my fingers crossed.
Enjoy Vietnam, it is a truly fantastic country!
Gail